1. Technical Field
The present disclosure relates to techniques, for example, for a display device such as a liquid crystal display device (LCD), for a touch sensor (also called a touch panel [TP]), for a liquid crystal display device with a touch sensor (in other words, a liquid crystal touch panel module), and for an electronic apparatus. The present disclosure particularly relates to a technique for a liquid crystal display device with an in-cell capacitive touch sensor.
2. Description of the Related Art
Examples of liquid crystal display devices with a touch sensor whose liquid crystal display function implements a touch sensor function, particularly for reducing thickness for example, include a liquid crystal display device with an in-cell touch sensor (called, for example, “in-cell touch LCD” or “in-cell liquid crystal touch panel”).
A liquid crystal display device with an in-cell capacitive touch sensor as a related example has an array substrate (also called a TFT substrate) and a color filter (CF) substrate that are elements constituting the liquid crystal display function, and a liquid crystal layer interposed between the array substrate and the CF substrate. The array substrate is provided with thin-film transistors (TFTs) including gate electrodes and source electrodes, pixel electrodes, retention capacitors, a common electrode, and the like. The CF substrate is provided with a color filter and the like. The liquid crystal display device with a touch sensor includes a touch drive electrode (transmitting electrode referenced as Tx) and a touch detection electrode (receiving electrode referenced as Rx) that are elements constituting the touch sensor function.
The above-described liquid crystal display device with a touch sensor particularly has a particular example configuration (called “combined use type”) in which an electrode unit and a wiring layer for the liquid crystal display function is partially used also as an electrode unit and a wiring layer for the touch sensor function. A configuration example is described, for example, in Japanese Patent Application Laid-open No. 2009-244958.
For example, in a configuration example (first related configuration example) of the combined use type liquid crystal display device with a touch sensor corresponding to a vertical electric field mode LCD, the array substrate includes a first electrode that is a first common electrode unit (referenced as COM1), and an electrode unit used as both a second common electrode unit (referenced as COM2) and the transmitting electrode Tx is configured as a second electrode on the inner side (on the side nearer to the liquid crystal layer) of the CF substrate, and the receiving electrode Rx is configured as a third electrode on the outer side (front surface) of the CF substrate.
In a configuration example (second related configuration example) of the combined use type liquid crystal display device with a touch sensor corresponding to a horizontal electric field mode LCD, an electrode unit used as both a common electrode (referenced as COM) and the transmitting electrode Tx is configured as a first electrode on the array substrate, and the receiving electrode Rx is configured as a second electrode on the CF substrate.
The horizontal electric field mode or the vertical electric field mode is applicable as a driving method for the above-mentioned liquid crystal layer. A fringe field switching (FFS) mode and an in-plane switching (IPS) mode are examples of the horizontal electric field mode. A twisted nematic (TN) mode, a vertical alignment (VA) mode, and an electrically controlled birefringence (ECB) mode are examples of the vertical electric field mode.
A general liquid crystal display device with a touch sensor includes a display area corresponding to a screen of a panel unit, and a frame portion disposed outside the display area. The display area is a region constituted by pixels and touch detection units. The frame portion is formed with, for example, a peripheral circuit. The peripheral circuit is formed by a process such as a chip-on-glass (COG) process or a low-temperature polycrystalline silicon (LTPS) process. The peripheral circuit is, for example, a driver that drives electrodes of the panel. Examples of the driver include, but are not limited to, a gate driver that drives gate electrodes and gate lines.
General issues and requirements in devices such as the above-described liquid crystal display device with a touch sensor includes, for example, thickness reduction, space saving, simplification in the production process and the number of parts, cost reduction by simplification, and improvement in quality of display and accuracy of touch detection. Regarding particularly the simplification, the number of layers is reduced to reduce cost by employing the combined use type in-cell configuration in which the electrodes and the wiring layers are used for both of the different functions as illustrated in the above-described configuration example. In addition, there are special requirements on space saving: the display area and a touch detection area corresponding to the display area are desirable to be as large as possible, and the frame portion and the like are desirable to be as small as possible, relative to the overall size of the device. Regarding the accuracy of touch detection, the screen serving as the touch detection area is desirable to have an appropriate and uniform degree of sensitivity of touch detection.
Related art examples regarding the above-described liquid crystal display device with a touch sensor includes Japanese Patent Application Laid-open No. 2012-73783. Japanese Patent Application Laid-open No. 2012-73783 describes how to obtain a display device with a touch detection function that is capable of enhancing uniformity in sensitivity of detection of touch. In particular, Japanese Patent Application Laid-open No. 2012-73783 describes that a plurality of drive electrodes extends to a first position or a second position located outside of the first position, the first position being away from the center of a touch detection electrode located outermost among a plurality of touch detection electrodes disposed in an effective display region S, by half the length of an arrangement pitch of the touch detection electrodes.
In the related in-cell capacitive liquid crystal touch panel, particularly in the combined use type configuration example (such as Japanese Patent Application Laid-open No. 2009-244958) in which the same electrode unit is used for both the liquid crystal display function and the touch sensor function, the touch detection area corresponding to the display area is desirable to have an appropriate and uniform degree of sensitivity of touch detection.